Testing of aqueous solutions

Abstract

Aqueous solutions such as chromium plating solutions are tested by contacting the solution with a water permeable medium such as a folded filter paper, causing the solution to diffuse upwardly through the medium and contacting separate portions of the diffusing solution in the medium with a water soluble ferrocyanide salt and with a water soluble iron salt respectively. The test may be performed when a filter paper, whose ends have been impregnated respectively with potassium ferrocyanide and a ferrous salt.

We claim: 
     
       1. A method of determining the presence in an aqueous electroplating electrolyte containing suspended solids of (i) excess trace metals which react with ferrocyanide or of (ii) excess ferrocyanide comprising contacting a portion of said electrolyte with a first portion of a water permeable cellulosic medium, said medium containing at least three portions, a first portion which is adapted to be contacted by said electrolyte and which is free of ferrocyanide and iron salts,   a second test portion which is impregnated with a water soluble ferrocyanide salt and is free from iron salt and is in contact with said first test portion, and   a third test portion which is impregnated with a water soluble iron salt and is free from ferrocyanide salt and is also in contact with said first portion,     whereby a first part of said electrolyte diffuses through said first portion which separates out suspended solids and then contacts said second portion and a second part of said electrolyte diffuses through said first portion and then contacts said third portion, to indicate whether said electrolyte contains an excess of (i) said trace metals or of (ii) ferrocyanide.   
     
     
       2. A method according to claim 1 wherein the cellulosic medium is filter paper. 
     
     
       3. A method according to claim 2 wherein the ferrocyanide salt is potassium ferrocyanide. 
     
     
       4. A method according to claim 2 wherein the iron salt is selected from the group consisting of ferrous chloride, ferrous sulphate and ferrous nitrate. 
     
     
       5. Means for testing aqueous solutions comprising a water permeable paper containing at least three portions, a first water permeable portion which is free of ferrocyanide and iron salts, said first portion being adapted to be immersed in the solution being tested, and second and third test portions, said second test portion being impregnated with a water soluble ferrocyanide salt and being free from iron salt, and said third test portion being impregnated with an iron salt and being free from ferrocyanide salt, each of said second and third portions being contiguous with a part of said first portion. 
     
     
       6. Testing means as claimed in claim 5 wherein the ferrocyanide salt is potassium ferrocyanide. 
     
     
       7. Testing means as claimed in claim 5 wherein the iron salt is selected from the group consisting of ferrous chloride, ferrous sulphate and ferrous nitrate. 
     
     
       8. Testing means according to claim 5 wherein the impregnated second and third portions are separated by said first portion.